Electromagnetic radiation transparent device and method of making thereof

ABSTRACT

A medical device includes a pattern of electrically conductive material. The pattern of electrically conductive material has an anti-antenna geometrical shape such that the anti-antenna geometrical shape substantially prevents the medical device from creating an imaging artifact and/or substantially allows imaging of a volume within the medical device. The pattern may be formed by multiple “figure-8” shaped electrical conductors, multiple “figure-8” emulating electrical conductors, multiple sine-wave-like shaped electrical conductors, multiple zig-zag patterned electrical conductors, by multiple electrical conductors, each having sequential conductive loops, and/or a single conductor weaved into a loop mesh. The electrically conductive material may be titanium, tantalum, nitinol, stainless steel, and/or NbZr.

PRIORITY INFORMATION

This application claims priority from U.S. Provisional PatentApplication, Ser. No. 60/497,591, filed on Aug. 25, 2003. The entirecontent of U.S. Provisional Patent Application, Ser. No. 60/497,591 ishereby incorporated by reference.

FIELD OF THE PRESENT INVENTION

The present invention is directed to stent designs, deployment devicesfor stents, and the fabrications thereof More particularly, the presentinvention is directed to stents which produce little or no magneticresonance image artifacts and the fabrications thereof.

BACKGROUND OF THE PRESENT INVENTION

The use of stents as a medical corrective and preventive device is wellknown.

For example, U.S. Pat. No. 5,133,732 discloses that a stent can beimplanted into a body vessel. The stent is a cylindrical body formed bya coiled generally continuous wire with a deformable zig-zag structure.The stent is further provided with means for preventing the stent bodyfrom stretching along its longitudinal axis. This stent is especiallyuseful when implanting very long stents by means of balloon expansion.The entire content of U.S. Pat. No. 5,133,732 is hereby incorporated byreference.

In another example, U.S. Pat. No. 5,507,767 discloses that aself-expanding endovascular stent is formed of stainless steel wirewhich is bent into an elongated zigzag pattern. The zigzag pattern has aplurality of substantially straight wire sections of various lengthsseparating a plurality of bends. The zigzag pattern is helically woundabout a central axis to define a tubular shape such that a majority ofthe bends is disposed in a helix. Adjacent bends in the helix areinterconnected with a filament. The entire content of U.S. Pat. No.5,507,767 is hereby incorporated by reference.

Magnetic resonance imaging (“MRI”) has been developed as an imagingtechnique adapted to obtain both images of anatomical features of humanpatients as well as some aspects of the functional activities andcharacteristics of biological tissue. These images have medicaldiagnostic value in determining the state of the health of the tissueexamined. Unlike the situation with fluoroscopic imaging, a patientundergoing magnetic resonance imaging procedure may remain in the activeimaging system for a significant amount of time, e.g. a half-hour ormore, without suffering any adverse effects.

In an MRI process, a patient is typically aligned to place the portionof the patient's anatomy to be examined in the imaging volume of the MRIapparatus. Such an MRI apparatus typically comprises a primaryelectromagnet for supplying a constant magnetic field (B₀) which, byconvention, is along the z-axis and is substantially homogeneous overthe imaging volume and secondary electromagnets that can provide linearmagnetic field gradients along each of three principal Cartesian axes inspace (generally x, y, and z, or x₁, x₂ and x₃, respectively). The MRIapparatus also comprises one or more RF (radio frequency) coils whichprovide excitation and detection of the MRI induced signals in thepatient's body.

The gradient fields are switched ON and OFF at different rates dependingon the MRI scan sequence used. In some cases, this may result in achanging magnetic field on the order of dB/dt=50 T/s. The frequency thata gradient field may be turned ON can be between 200 Hz to about 300kHz.

Uniformity in the static magnetic B₀ field over the imaging volume isimportant for image clarity. When the field is not uniform, imagedistortions called “image artifacts” result. Additionally, if thegradient fields deviate significantly from their ideal linear characterover the imaging volume, image artifacts develop.

Medical devices which are placed into a patient's body can cause themagnetic fields of the MRI system to deviate from their preferredcharacteristics for clear imaging. If a medical device comprisesmetallic components (such as iron), image artifacts result due to themetal's magnetic susceptibility properties distorting the MRI systemapplied magnetic fields. These are known as susceptibility artifacts.Additionally, if the medical device comprises conductive components,eddy currents develop in these conductive components when the MRIsystem's oscillating magnetic fields are applied. The eddy currentsdistort the net magnetic fields in the imaging volume, thereby providinganother source for MR imaging artifacts.

After a stent is inserted into a patient, it is often desirable, overtime, to determine if the stent is performing as expected. In the case,for example, of deploying a stent to correct a stenosis problem, it isdesirable to determine if there is any indication of restenosis. This,as well as for other medical situations, requires obtaining images ofthe volume inside the stent. Due to the image artifact problems,described above, inherent in metallic, conductive stents, it is notpossible to obtain clear MR images of the interior volume of the stents.

Attempts have been made to overcome these problems. The article,“Artifact-Free In-Stent Lumen Visualization by Standard MagneticResonance Angiography Using a New Metallic Magnetic Resonance ImagingStent” by Arno Buecker, et al., Circulation, Apr. 16, 2002, pp.1772-1775, discloses that a handmade stent can enhance the imagingability of the stent's lumen. However, the handmade prototypes lacked aradial force comparable to standard stainless steel stents.Additionally, the article discloses the use of a contrasting agent toenhance visualization of the stent lumen.

The article “MR Imaging of Vascular Stents: Effects of Susceptibility,Flow, and Radiofrequency Eddy Currents” by Lambertus W. Bartels, et al.,published in Journal of Vascular and Interventional Radiology, volume12, Number 3, March 2001, pp. 365-371, describes the various imageartifacts that prevent clear imaging of stent lumen.

The article “Improved Lumen Visualization in Metallic Vascular Implantsby Reducing RF Artifacts” by Lambertus W. Bartels, et al., published inMagnetic Resonance in Medicine, 74:171-180 (2002), describes attempts atimaging metallic stents lumen by using contrast agents and by increasingthe power deposited into the patient during the MRI procedure. The powerdeposited into the patient body, measured as the Specific AbsorptionRate (SAR) can be harmful to the patient undergoing an MRI if set toohigh. In addition to the higher power deposited into the patient, thearticle discloses that adjustments in the image reconstruction processneed to be implemented.

U.S. patent application Publication US 2002/0188345 A1, published Dec.12, 2002, discloses an expandable metallic stent that hasdiscontinuities of non-conducting material. These eliminate electricallyconducting paths in the stent rings and cells. This makes the stenteasier to image with magnetic resonance imaging (MRI). The entirecontent of U.S. patent application Publication US 2002/0188345 A1 ishereby incorporated by reference.

WIPO PCT publication WO 03/015662 A1 discloses that a metallicendoprosthesis causes no significant artifacts on images taken bymagnetic resonance tomography (MRT), as a result of the combination ofthe production materials with a special design, which permits anevaluation of the externally adjacent region and the lumen of theendoprosthesis by means of MRT.

Although the above-described stents can be used to help a patient, thesestents still cause magnetic resonance imaging artifacts. Moreover, theabove-described stents prevent the imaging of the volume within thestent during magnetic resonance imaging.

Therefore, it is desirable to provide a stent which produces little tono magnetic resonance imaging artifacts. Moreover, it is desirable toprovide a stent that allows the imaging of the volume within the stent.Furthermore, it is desirable to provide a stent which produces little tono magnetic resonance imaging artifacts and/or allows the imaging of thevolume within the stent.

SUMMARY OF THE PRESENT INVENTION

One aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material has an anti-antennageometrical shape such that the anti-antenna geometrical shapesubstantially prevents the medical stent from creating an imagingartifact.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material has an anti-antennageometrical shape such that the anti-antenna geometrical shapesubstantially allows imaging of a volume within the stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material has an anti-antennageometrical shape such that the anti-antenna geometrical shapesubstantially prevents the medical stent from creating an imagingartifact and substantially allows imaging of a volume within the stent.

Another aspect of the present invention is an electrically conductivestructure. The electrically conductive structure includes a pattern ofelectrically conductive material. The pattern of electrically conductivematerial has an anti-antenna geometrical shape such that theanti-antenna geometrical shape substantially prevents creation of animaging artifact by the electrically conductive structure.

Another aspect of the present invention is a medical device. The medicaldevice includes a pattern of electrically conductive material. Thepattern of electrically conductive material has an anti-antennageometrical shape such that the anti-antenna geometrical shapesubstantially prevents creation of an imaging artifact by the medicaldevice.

Another aspect of the present invention is an electrically conductivestructure. The electrically conductive structure includes a pattern ofelectrically conductive material. The pattern of electrically conductivematerial has an anti-antenna geometrical shape such that theanti-antenna geometrical shape substantially allows imaging of a volumewithin the electrically conductive structure.

Another aspect of the present invention is an electrically conductivestructure. The electrically conductive structure includes a pattern ofelectrically conductive material. The pattern of electrically conductivematerial has an anti-antenna geometrical shape such that theanti-antenna geometrical shape substantially prevents creation of animaging artifact by the medical device and substantially allows imagingof a volume within the electrically conductive structure.

Another aspect of the present invention is a medical device. The medicaldevice includes a pattern of electrically conductive material. Thepattern of electrically conductive material has an anti-antennageometrical shape such that the anti-antenna geometrical shapesubstantially allows imaging of a volume within the medical device.

Another aspect of the present invention is a medical device. The medicaldevice includes a pattern of electrically conductive material. Thepattern of electrically conductive material has an anti-antennageometrical shape such that the anti-antenna geometrical shapesubstantially prevents creation of an imaging artifact by the medicaldevice and substantially allows imaging of a volume within the medicaldevice.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially prevents themedical stent from creating an imaging artifact.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially allows imagingof a volume within the stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially prevents themedical stent from creating an imaging artifact and substantially allowsimaging of a volume within the stent.

Another aspect of the present invention is an electrically conductivestructure. The electrically conductive structure includes a pattern ofelectrically conductive material. The pattern of electrically conductivematerial substantially prevents creation of an imaging artifact by theelectrically conductive structure.

Another aspect of the present invention is a medical device. The medicaldevice includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially preventscreation of an imaging artifact by the medical device.

Another aspect of the present invention is an electrically conductivestructure. The electrically conductive structure includes a pattern ofelectrically conductive material. The pattern of electrically conductivematerial substantially allows imaging of a volume within theelectrically conductive structure.

Another aspect of the present invention is an electrically conductivestructure. The electrically conductive structure includes a pattern ofelectrically conductive material. The pattern of electrically conductivematerial substantially prevents creation of an imaging artifact by themedical device and substantially allows imaging of a volume within theelectrically conductive structure.

Another aspect of the present invention is a medical device. The medicaldevice includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially allows imagingof a volume within the medical device.

Another aspect of the present invention is a medical device. The medicaldevice includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially preventscreation of an imaging artifact by the medical device and substantiallyallows imaging of a volume within the medical device.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially prevents themedical stent from creating an imaging artifact. The electricallyconductive material is shaped so as to be expandable, the expansion ofthe electrically conductive material causing an increase in a radius ofthe medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially allows imagingof a volume within the stent. The electrically conductive material isshaped so as to be expandable, the expansion of the electricallyconductive material causing an increase in a radius of the medicalstent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially prevents themedical stent from creating an imaging artifact and substantially allowsimaging of a volume within the stent. The electrically conductivematerial is shaped so as to be expandable, the expansion of theelectrically conductive material causing an increase in a radius of themedical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially prevents themedical stent from creating an imaging artifact. The electricallyconductive material is shaped so as to be expandable upon application ofheat, the expansion of the electrically conductive material causing anincrease in a radius of the medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially allows imagingof a volume within the stent. The electrically conductive material isshaped so as to be expandable upon application of heat, the expansion ofthe electrically conductive material causing an increase in a radius ofthe medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material. Thepattern of electrically conductive material substantially prevents themedical stent from creating an imaging artifact and substantially allowsimaging of a volume within the stent. The electrically conductivematerial is shaped so as to be expandable upon application of heat, theexpansion of the electrically conductive material causing an increase ina radius of the medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material and atrack-and-lock mechanism having a shape substantially matching the shapeof the electrically conductive material so as to substantially preventthe electrically conductive material from moving in such a way as toreduce the radius of the medical stent. The pattern of electricallyconductive material substantially prevents the medical stent fromcreating an imaging artifact. The electrically conductive material isshaped so as to be expandable, the expansion of the electricallyconductive material causing an increase in a radius of the medicalstent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material and atrack-and-lock mechanism having a shape substantially matching the shapeof the electrically conductive material so as to substantially preventthe electrically conductive material from moving in such a way as toreduce the radius of the medical stent. The pattern of electricallyconductive material substantially allows imaging of a volume within thestent. The electrically conductive material is shaped so as to beexpandable, the expansion of the electrically conductive materialcausing an increase in a radius of the medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material and atrack-and-lock mechanism having a shape substantially matching the shapeof the electrically conductive material so as to substantially preventthe electrically conductive material from moving in such a way as toreduce the radius of the medical stent. The pattern of electricallyconductive material substantially prevents the medical stent fromcreating an imaging artifact and substantially allows imaging of avolume within the stent. The electrically conductive material is shapedso as to be expandable, the expansion of the electrically conductivematerial causing an increase in a radius of the medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material and atrack-and-lock mechanism having a shape substantially matching the shapeof the electrically conductive material so as to allow the electricallyconductive material to move in a single direction. The pattern ofelectrically conductive material substantially prevents the medicalstent from creating an imaging artifact. The electrically conductivematerial is shaped so as to be expandable, the expansion of theelectrically conductive material causing an increase in a radius of themedical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material and atrack-and-lock mechanism having a shape substantially matching the shapeof the electrically conductive material so as to allow the electricallyconductive material to move in a single direction. The pattern ofelectrically conductive material substantially allows imaging of avolume within the stent. The electrically conductive material is shapedso as to be expandable, the expansion of the electrically conductivematerial causing an increase in a radius of the medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a pattern of electrically conductive material and atrack-and-lock mechanism having a shape substantially matching the shapeof the electrically conductive material so as to allow the electricallyconductive material to move in a single direction. The pattern ofelectrically conductive material substantially prevents the medicalstent from creating an imaging artifact and substantially allows imagingof a volume within the stent. The electrically conductive material isshaped so as to be expandable, the expansion of the electricallyconductive material causing an increase in a radius of the medicalstent.

Another aspect of the present invention is a medical stent. The medicalstent includes a plurality of links, each link being connected togetherso as to form a cylindrical shaped medical stent, each link being shapedso as to be expandable, the expansion of the links causing an increasein a radius of the medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a plurality of links, each link being connected togetherso as to form a cylindrical shaped medical stent, each link being shapedso as to be expandable upon application of heat, the expansion of thelinks causing an increase in a radius of the medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a plurality of links, each link being connected togetherso as to form a cylindrical shaped medical stent, each link being shapedso as to be expandable, the expansion of the links causing an increasein a radius of the medical stent; and a track-and-lock mechanism havinga shape substantially matching the shape of the links so as tosubstantially prevent the links from moving in such a way as to reducethe radius of the medical stent.

Another aspect of the present invention is a medical stent. The medicalstent includes a plurality of links, each link being connected togetherso as to form a cylindrical shaped medical stent, each link being shapedso as to be expandable upon application of heat, the expansion of thelinks causing an increase in a radius of the medical stent; and atrack-and-lock mechanism having a shape substantially matching the shapeof the links so as to allow the links to move in a single direction.

Another aspect of the present invention is a method of fabricating amedical stent. The method cuts a first cylinder of electricallyconductive material so as to create a first pattern of conductive meshstrands having a plurality of nodes; cuts a second cylinder ofelectrically conductive material so as to create a first pattern ofconductive mesh strands having a plurality of nodes; positions the firstcylinder into a volume of the second cylinder and positioning the firstcylinder with respect to the second cylinder such the nodes of the firstcylinder are close to the nodes of the second cylinder without the nodesof the first cylinder touching the nodes of the second cylinder, andapplies a non-conductive binding material to adjacent nodes of the twocylinders.

Another aspect of the present invention is a method of fabricating amedical stent. The method cuts a first cylinder of electricallyconductive material so as to create a first pattern of conductive meshstrands having a plurality of nodes; cuts a second cylinder ofelectrically conductive material so as to create a first pattern ofconductive mesh strands having a plurality of nodes; positions the firstcylinder into a volume of the second cylinder and positioning the firstcylinder with respect to the second cylinder such the nodes of the firstcylinder are close to the nodes of the second cylinder without the nodesof the first cylinder touching the nodes of the second cylinder;positions a third cylinder of a non-conductive binding material betweenthe first and second cylinders; and applies heat to the adjacent nodesof the first and second cylinders to cause the non-conductive bindingmaterial to bind the adjacent nodes together.

Another aspect of the present invention is a method of fabricating amedical stent. The method produces a web of conductive strands whereinat all the cross-over points, a non-conductive material is applied tohold the cross-over point strands in place and to electrically isolatethe conductive strands from one another; cuts a portion of the web toproduce a sheet of conductive strands; forms the sheet of conductivestrands into a cylinder shape; and attaches ends of sheet together tohold the cylinder shape in place.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may take form in various components andarrangements of components, and in various steps and arrangements ofsteps. The drawings are only for purposes of illustrating a preferredembodiment and are not to be construed as limiting the presentinvention, wherein:

FIG. 1 is a schematic illustration of two conductive loops in a changingmagnetic field;

FIG. 2 is a schematic illustration of a conductor in a “figure-8”configuration in a changing magnetic field;

FIG. 3 is an illustration of one stent embodiment according to theconcepts of the present invention;

FIG. 4 is an illustration of another stent embodiment according to theconcepts of the present invention;

FIG. 5 is an illustration of another stent embodiment according to theconcepts of the present invention;

FIG. 6 is an illustration of another stent embodiment according to theconcepts of the present invention;

FIG. 7 illustrates a curved stent mesh embodiment according to theconcepts of the present invention;

FIGS. 8 and 9 illustrate a stent mesh by a “Z”-like shape strandaccording to the concepts of the present invention;

FIG. 10 illustrates a stent mesh embodiment according to the concepts ofthe present invention;

FIG. 11 illustrates a cross-over node in a stent mesh according to theconcepts of the present invention;

FIG. 12 illustrates another cross-over node in a stent mesh according tothe concepts of the present invention;

FIG. 13 illustrates another stent embodiment according to the conceptsof the present invention;

FIG. 14 illustrates a stent within a body which is heated by applicationof external RF energy;

FIG. 15 is a cross sectional view of a coated stent according to theconcepts of the present invention;

FIGS. 16 through 21 illustrate various steps in the creation of amedical stent according to the concepts of the present invention;

FIGS. 22 through 24 illustrate the use of a planar conductive weavesheet material from which a stent is formed according to the concepts ofthe present invention; and

FIGS. 25 and 26 illustrate a locking mechanism for an expandable stentaccording to the concepts of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention will be described in connection with preferredembodiments, however, it will be understood that there is no intent tolimit the present invention to the embodiments described herein. On thecontrary, the intent is to cover all alternatives, modifications, andequivalents as may be included within the spirit and scope of thepresent invention, as defined by the appended claims.

For a general understanding of the present invention, reference is madeto the drawings. In the drawings, like reference have been usedthroughout to designate identical or equivalent elements. It is alsonoted that the various drawings illustrating the present invention arenot drawn to scale and that certain regions have been purposely drawndisproportionately so that the features and concepts of the presentinvention could be properly illustrated.

FIG. 1 is a schematic illustration of induced currents 110 and 112 intwo conductive rings 102 and 104, respectively, when the conductiverings 102 & 104 are placed in an environment in which there is anoscillating magnetic field 106. At an instant in time, as illustrated inFIG. 1, both currents 110 & 112 travel in a clockwise direction. But asthe magnetic field oscillates, the direction of these currents 110 & 112will diminish to zero and then begin to circulate in a counter-clockwisedirection (not shown.)

FIG. 2 illustrates when the conductive rings 102 & 104 have beenelectrically joined together to form a single “figure-8” shaped oremulating conductor 120. The two lobes 126 & 128 of the “figure-8”shaped or emulating conductor 120 have equal planar areas. When placedin changing magnetic field 122 such that the flux of the magnetic field122 passes through the lobes 126 & 128, no net current will be inducedin the “figure-8” shaped or emulating conductor 120. The “figure-8”shaped or emulating conductor 120 is electrically insulated at thecross-over point 124.

FIG. 3 illustrates a portion of a medical stent 130, according to theconcepts of the present invention. The illustrated medical stent 130includes multiple “figure-8” shaped or emulating conductors 132, 134,136 & 138. The “figure-8” shaped or emulating conductors 132, 134, 136 &138 are electrically insulated at the cross-over points 131. Thecross-over points 131 may also provide mechanical support for the“figure-8” shaped or emulating conductors 132, 134, 136 & 138

The “figure-8” shaped or emulating conductors 132, 134, 136 & 138 arefastened together by non-conductive connectors 140. These connectors 140may be constructed of Teflon®, Tefzel®, a nonconductive polymer,silicon, or other nonconductive material. The “figure-8” shaped oremulating conductors 132, 134, 136 & 138 may be, for example, tantalum,nitinol, copper, or other conductive material or conductive compositematerial, which has a low magnetic susceptibility.

The “figure-8” shaped or emulating conductors realize immunity from theelectromagnetic interference or insult. In other words, each “figure-8”shaped or emulating conductor has an anti-antenna geometrical shape suchthat the anti-antenna geometrical shape prevents the medical stent fromcreating an imaging artifact and/or allows the imaging of the volumewithin the stent.

FIG. 4 illustrates a portion of a medical stent 160, according to theconcepts of the present invention. The illustrated medical stent 160includes conductors 162 & 164 having sequential conductive loops to formthe cylindrical surface of the medical stent 160. The sequentialconductive loops form two or more sequential “figure-8” shaped oremulating conductive loop pairs wherein each sequentially loopedconductor 162 & 164 contains an even number of loops.

At crossover point 168, the conductor 164 is electrically isolated by aninsulation member 165 to prevent short circuiting the overall loopsequence. At crossover point 169, the conductor 162 is electricallyisolated by an insulation member 167 to prevent short circuiting theoverall loop sequence. The insulation members 165 and 167, at thecrossover points 168 & 169, can also provide mechanical support forconductors 162 & 164 so that the shape is maintained.

The sequentially looped conductors 162 & 164 are fastened to each otherusing non-conductive material 166. Material 166 also provides means forsecuring the sequentially looped conductor 162 & 164 from slippingthrough the fasteners 166. Additional sequentially looped conductors(not shown) are added to complete the stent construction.

The sequentially looped conductors realize immunity from theelectromagnetic interference or insult. In other words, eachsequentially looped conductor has an anti-antenna geometrical shape suchthat the anti-antenna geometrical shape prevents the medical stent fromcreating an imaging artifact and/or allows the imaging of the volumewithin the stent.

FIG. 5 illustrates a portion of a medical stent 170, according to theconcepts of the present invention. The illustrated medical stent 170includes a single conductor 172 weaved into a loop mesh to define thestent cylinder. The weave, for example, beginning at 174, traces downthe length of the to-be-constructed stent cylinder 170 and then back upthe cylinder length to define an even number of loops. The patternformed by the weave may be sinusoidal, “Z” shaped, zig-zag shaped, orsawtooth shaped or other such pattern that traverses back and forth withrespect to a direction that is perpendicular to the progressivedirection of travel of the trace. This pattern forms two or more runs oftwo or more sequential “figure-8” shaped or emulating conductive looppairs wherein each run of two or more sequential “figure-8” shaped oremulating conductive loop pairs contains an even number of loops.

Continuing to follow the weave pattern, the conductor 172 continues toweave down and up the length of the cylinder to the point 176. Tocomplete the stent, the weave continues in a like fashion around thecircumference of the yet to-be-defined cylinder stent 170.

At each intra-run cross-over point 178, a nonconductive material 179 isused to electrically insulate the conductor 172 from itselfAdditionally, the nonconductive material 179 secures the crossed-overconductor, along a run, from deforming or slipping or otherwise changingthe intra-run cross-over points.

At each inter-run cross-over point 175, a nonconductive material 177 isused to electrically insulate the conductor 172 from itselfAdditionally, the nonconductive material 177 secures the crossed-overconductor, between runs, from deforming or slipping or otherwisechanging the inter-run cross-over points.

The weave pattern of the conductor realizes immunity from theelectromagnetic interference or insult. In other words, the weavepattern has an anti-antenna geometrical shape such that the anti-antennageometrical shape prevents the medical stent from creating an imagingartifact and/or allows the imaging of the volume within the stent.

FIG. 6 illustrates a portion of a cylinder shaped stent 190 beingconstructed from a single conductive material 192 in a weave pattern. Inthis case, the conductor completes a circumferential sine-wave-likepattern rather than the longitudinal sine-wave-like pattern shown inFIG. 5.

It is noted that the circumferential pattern formed by the weave mayalso be sawtooth or other such pattern that traverses back and forthwith respect to a direction that is perpendicular to the progressivedirection of travel of the trace.

At intra-run cross-over points 194 & 198, nonconductive materials 191 &193 are used to electrically insulate the conductive material 192 fromitself Additionally, the nonconductive materials 191 & 193 secure thecrossed-over conductive material 192, along a run, from deforming orslipping or otherwise changing the intra-run cross-over points.

At each inter-run cross-over point 196, a nonconductive material 195 isused to electrically insulate the conductive material 192 from itselfAdditionally, the nonconductive material 195 secures the crossed-overconductive material 192, between runs, from deforming or slipping orotherwise changing the inter-run cross-over points.

The circumferential pattern realizes immunity from the electromagneticinterference or insult. In other words, the circumferential pattern hasan anti-antenna geometrical shape such that the anti-antenna geometricalshape prevents the medical stent from creating an imaging artifactand/or allows the imaging of the volume within the stent.

FIGS. 7-9 illustrate how the curved segments of the sine-wave like shapeof the weaves mentioned in FIGS. 3, 4, 5, and 6 can be replaced by “Z”shaped, zig-zag shaped, or sawtooth shaped segments.

FIG. 7 shows a typical cross-over point of a stent weave. Conductors 200and 202 (or a single conductor) of a stent weave are fastened togetherby a non-conductive material 201 which electrically insulates theconductors 200 and 202 (or a single conductor) from each other. It isnoted that conductors 200 and 202 are continuous, not discontinuous,through non-conductive material 201.

FIG. 8 shows one possible alternative to the curved weave segments 200and 202 of FIG. 7. In FIG. 8, the conductive segments have a “Z” shaped,zig-zag shaped, or sawtooth shaped. The conductive segments 204 and 206do not cross over each other. The conductive segments 204 and 206 arefastened to each other by material 208 which electrically isolatesconductive segments 204 and 206 from each other.

When the stent is to be positioned and expanded in the body, the “Z”shaped segments of conductive segments 204 and 206 straighten out toincrease the overall diameter of the cylinder defined by the stent. Thisis shown in FIG. 9 wherein the conductive segments 204 and 206 have beenstraightened, thus increasing their span length and the overall diameterof the cylinder defined by the stent.

FIG. 10 shows a conductive cylinder medical stent 220 mesh comprisingmany conductive strands 221 and junctions 222. In this case, theconductors complete a sine-wave-like pattern. The pattern formed by theconductors may be circumferential or longitudinal. It is noted that thepattern formed by the conductors may also be “Z” shaped, zig-zag shaped,or sawtooth shaped or other such pattern that traverses back and forthwith respect to a direction that is perpendicular to the progressivedirection of travel of the trace.

The pattern formed by the conductors realizes immunity from theelectromagnetic interference or insult. In other words, the patternformed by the conductors has an anti-antenna geometrical shape such thatthe anti-antenna geometrical shape prevents the medical stent fromcreating an imaging artifact and/or allows the imaging of the volumewithin the stent.

FIG. 11 illustrates an expanded view of a junction 222, according to theconcepts of the present invention. The junction 222 includes fourconductive strands 224, 226, 228 & 230 fastened together andelectrically isolated from one another by the non-conductive material234. Small holes 225, 227, 229 & 231 are optionally fabricated into theends of the conductive strands 224, 226, 228 & 230 so that the fasteningmaterial 234 may be shaped to include protrusions to securely fasten tothe strands 224, 226, 228 & 230 with no possibility of any of thestrands slipping out of the material 234.

It is noted that, although not shown, certain ends of the conductivestrands 224, 226, 228 & 230 may be electrically connected to each otherto form the proper loop circuitry needed to produce the opposingcurrents in the stent so that a net zero current is realized. Forexample, conductive strand 224 may be electrically connected toconductive strand 230, while conductive strand 226 may be electricallyconnected to conductive strand 228. On the other hand, for anotherexample, conductive strand 224 may be electrically connected toconductive strand 226, while conductive strand 230 may be electricallyconnected to conductive strand 228.

The connection pattern of certain ends of the conductive strandsrealizes immunity from the electromagnetic interference or insult. Inother words, the connection pattern of certain ends of the conductivestrands has an anti-antenna geometrical shape such that the anti-antennageometrical shape prevents the medical stent from creating an imagingartifact and/or allows the imaging of the volume within the stent.

Other shapes for the conductive strand ends to help secure theconductive strands 224, 226, 228 & 230 together, while keeping theconductive strands 224, 226, 228 & 230 electrically isolated, may beused. For example, FIG. 12 shows the conductive strands 224, 226, 228 &230 with barbed ends 240, 242, 246 & 248, respectively, so that thefastening material 234 may be shaped around the barbed ends 240, 242,246 & 248 to securely fasten to the strands 224, 226, 228 & 230 with nopossibility of any of the strands slipping out of the material 234.

It is noted that, although not shown, certain of the barbed ends 240,242, 246 & 248 of the conductive strands 224, 226, 228 & 230 may beelectrically connected to each other to form the proper loop circuitryneeded to produce the opposing currents in the stent so that a net zerocurrent is realized. For example, conductive barbed end 240 may beelectrically connected to conductive barbed end 242, while conductivebarbed end 246 may be electrically connected to conductive barbed end248. On the other hand, for another example, conductive barbed end 240may be electrically connected to conductive barbed end 246, whileconductive barbed end 248 may be electrically connected to conductivebarbed end 242.

The connection pattern of certain barbed ends of the conductive strandsrealizes immunity from the electromagnetic interference or insult. Inother words, the connection pattern of certain barbed ends of theconductive strands has an anti-antenna geometrical shape such that theanti-antenna geometrical shape prevents the medical stent from creatingan imaging artifact and/or allows the imaging of the volume within thestent.

FIG. 13 illustrates another type of conductive stent weave which can beemployed as a stent or as a component of a stent. The conductor 260 isformed to produce a loop 261 that would have induced current flowing ina first direction, a loop 264 that would have induced current flowing ina second direction, a loop 266 that would have induced current flowingin the first direction, and a loop 268 that would have induced currentflowing in the second direction, the first direction being opposite ofthe second direction. The direction changing pattern 263 enables theadjacent loops to have induced currents flowing in opposite directions.

An example of such a configuration is a loop-½ hitch-loop-½ hitchpattern wherein the ½ hitch would correspond to the direction changingpattern 263 of FIG. 13.

As illustrated in FIG. 13, stacking such loops 261, 264, 266, 268 . . ., with the interspersed direction changing pattern 263, forms acylindrical coil. In this way, when following the conductor 260 from oneend to the other, a trace would travel clockwise around the first loop261, counter-clockwise around the next loop 264, clockwise around thenext 266, counter-clockwise around the next 268, and so on.

At each cross-over point, nonconductive materials 267 & 265 are used toelectrically insulate the conductive material 260 from itselfAdditionally, the nonconductive materials 267 & 265 secure thecrossed-over conductive material 260 from deforming or slipping orotherwise changing the cross-over points.

Optionally, non-conductive structural ribbing 262 may also be added toincrease the structure strength and integrity of the overall stent.

The stacked loop pattern, with interspersed direction changing pattern,realizes immunity from the electromagnetic interference or insult. Inother words, the stacked loop pattern, with interspersed directionchanging pattern, has an anti-antenna geometrical shape such that theanti-antenna geometrical shape prevents the medical stent from creatingan imaging artifact and/or allows the imaging of the volume within thestent.

FIG. 14 illustrates the deployment of an arterial stent 302. Thearterial stent 302 is initially attached to a guidewire 306 at itsdistal end 304 and is positioned into place within a body 310 and withinan artery 308. The arterial stent 302 is fabricated out of a memorymaterial, for example, nitinol which, when heated, returns to a previousmanufactured shape.

Initially the arterial stent 302 has a small cylindrical diameter. WhenRF energy 312 is transmitted through the body 310, the arterial stent302 will heat up and expand to its final deployed diameter.

In one embodiment, the distal end 304 of the guidewire 306 is coatedwith a material which is particularly efficient at converting the RFenergy 312 into heat energy to heat and activate the stent 302expansion.

In another embodiment, the arterial stent 302, which may be a mesh orweave like stent as describe above, is coated with a material 322 (seeFIG. 15) which is particularly efficient at converting the RF energy 312(see FIG. 15) into heat energy. It is noted that the arterial stent 302should be constructed to realize immunity from the electromagneticinterference or insult. In other words, the arterial stent 302 should beconstructed to have an anti-antenna geometrical shape such that theanti-antenna geometrical shape prevents the medical stent from creatingan imaging artifact and/or allows the imaging of the volume within thestent.

FIG. 15 shows a cross-section of the arterial stent 302 which iscomprised of the stent mesh shape memory material 320 coated withheating material 322. Alternatively, only the outside of the stent mesh320 is coated with the heating material 322. Alternatively, only theinside of the stent mesh 320 is coated with the heating material 322.

The RF energy 312 may be that which is transmitted by an MRI system (notshown) or may be that from some other RF transmitter (not shown). It isknown that in some cases and under some conditions long conductors in anMRI environment can heat up. When this phenomenon is incorporated intothe catheter or guide-wire which is part of the overall stent deliverysystem, this heat energy can be utilized to activate the shape memorymaterial expansion, thus expanding the stent.

FIG. 16-21 illustrate one possible fabrication process for a medicalstent. Referring to FIG. 16, the initial stock material 349, forexample, tantalum; is in the shape of a hollow cylinder. The cylindermay be cut into a pattern as illustrated in FIG. 17, for example. Thecutting of the cylinder stock material 349 may be accomplished by lasercutting or by other means.

FIG. 17 shows the resulting cut cylinder 351 which comprises end rings350 and 354, and one half of the stent pattern mesh strands 356, 358 &360. (Other mesh strands are shown as dashed lines for clarity.)

The mesh strands 356, 358 & 360 are connected to the end rings 350 & 354by tabs 362 & 364.

FIG. 18 shows two such cut cylinders 351 positioned such that onecylinder has been rotated by 180 degrees; so that the two end rings 354are close to each other. As the arrows 355 in FIG. 18 illustrate, onecylinder is to be slid into the other. This may be accomplished inseveral different ways including: heating one of the cut cylinders sothat it expands and/or fabricating one of the two cut cylinders out acylinder stock material which is slightly smaller in diameter than theother.

FIG. 19 illustrates the two cut cylinders in their final position. Theorientation is such that the nodes in the cut pattern 381 & 382 areclose together, but are not touching.

The two cut cylinders realize immunity from the electromagneticinterference or insult. In other words, the two cut cylinders have ananti-antenna geometrical shape such that the anti-antenna geometricalshape prevents the medical stent from creating an imaging artifactand/or allows the imaging of the volume within the stent.

FIG. 20 illustrates the application of a non-conductive binding material390, for example, silicon rubber or other thermoplastic or thermosetpolymer, or glass, etc. at each of the nodes 381 & 382 which rigidlyfasten the conductive mesh strands 356, 358 & 360 together. Theresulting stent mesh 388 is then cut from the supporting nubs 362 & 364of FIG. 17, giving the final stent portion 388 shown in FIG. 21.

The pattern that is cut out of the initial hollow cylinder stock of FIG.16 may alternatively include “Z” shaped, zig-zag shaped, or sawtoothshaped segments as shown in FIG. 8 which facilitates the final stent'sability to expand radially.

In one embodiment (not shown, but referring to FIG. 21), thenon-conductive binding material 390 of FIG. 20 is initially in the formof a hollow cylinder which is so dimensioned as to fit between the twocut cylinders 351 forming three concentric cylinders, the bindingmaterial 390 cylinder being the middle layer. The application of a laseror other means then melts the binding material 390 at the nodes as wellas eliminates unwanted binding material.

In one embodiment, the weaving of the conductive material (see, forexample, FIG. 5) is used to produce a sheet stock planar material 400illustrated in FIG. 22. As mentioned for other conductive weaves (seedescription of FIG. 5), at all the cross-over points, non-conductivematerials 401 and 403 is applied to hold the cross-over point strands inplace and to electrically isolate the conductive strands from oneanother. A portion 406 of the planar woven sheet or web is cut from theinitial woven sheet 400. The dashed lines 402 and 404 indicate where acut through the woven sheet or web 400 is made.

FIGS. 23 and 24 show the cut portion 406 being rolled into a cylindershape. The cut strand, which come together as the cut edges 402 and 404,are brought together and then attached to one another to hold the stenttogether. The attachment may be affected by either a conductive material(solder, welding, etc.) or by a non-conductive means (glass, polymer,etc.)

In one embodiment (not shown) conductive metallic stents are coated witha nano-magnetic thin film coating which reduces the amount of eddycurrents generated by the oscillating magnetic fields of an MRI system.In one such embodiment, multiple lays of various compositions and/orthicknesses are applied to the stents. In another embodiment, onlyportions of the stent are coated with the nano-magnetic thin films, thuschanging the MRI system induced eddy current flow pattern.

In one embodiment, non-magnetic stents are coating with a nano-magneticthin film coating which alters the magnetic fields of the MRI systemenough for the stent to be visible in an MR image without distorting theimage of the tissue a short distance from the stent.

In another embodiment (not shown) conductive metallic stent is coatedwith a carbon composite material, in part, in patterns, or in whole.

In another embodiment (not shown) non-conductive stents are coated witha carbon composite material, in part, in patterns, or in whole.

FIGS. 25 and 26 illustrate a stent 500 which is, initially, at itssmallest radius “r” 501. The stent 500 is in the shape of a cylinder.

FIG. 25 illustrates a cross section of the stent 500. A stent strand 512is wrapped within the stent 500 to reduce the cylindrical radius 501before deployment with a body. The stent 500 has a track-and-lockmechanism 502 through which stent strand 512 passes and is confined to.

FIG. 26 gives one example of a track-and-lock mechanism 502. A portion506 of the track-and-lock mechanism 502 is shown as a cut-away view inFIG. 26. The stent strand 512 has teeth which match that of the teeth510 within the track-and-lock mechanism 502. The stent strand 512 isconfined to move in the guide slot 514 and can only move in such a wayso as to increase the overall radius 501 of the cylinder stent 500.

The shape of the teeth of the stent strand 512 and the shape of theteeth of the track-and-lock mechanism 502 prevent the stent strand 512from moving in such a way as to reduce the cylinder radius 501. Thus,when deployed with, e.g. a balloon catheter system (not shown); thestent may be expanded to its full and final radius and locked into thatradius.

In summary, the various stent embodiments, described above, realizeimmunity from the electromagnetic interference or insult. In otherwords, the stent has an anti-antenna geometrical shape such that theanti-antenna geometrical shape prevents the medical stent from creatingan imaging artifact and/or allows the imaging of the volume within thestent.

Although the various embodiments discussed above have been described inthe context of a medical stent, the various concepts and aspects of thepresent invention are readily applicable to other devices and uses.

For example, the pattern of electrically conductive material, accordingto the various concepts of the present invention, can be used in medicaldevices having electrically conductive structures that would, undernormal circumstances, generate imaging artifacts and/or heat in responseto the imaging processes, such as magnetic radiation imaging (MRI),and/or radio frequency radiation so as to make the medical devicesimaging artifact immune and heat resistant. More specifically, thepattern of electrically conductive material, according to the variousconcepts of the present invention, could be used to create an imagingartifact immune and heat resistant mail for a doctor's glove orclothing.

While various examples and embodiments of the present invention havebeen shown and described, it will be appreciated by those skilled in theart that the spirit and scope of the present invention are not limitedto the specific description and drawings herein, but extend to variousmodifications and changes.

1. A medical stent, comprising: a plurality of links, each link beingconnected together so as to form a cylindrical shaped medical stent,each link being shaped so as to be expandable, said expansion of saidlinks causing an increase in a radius of the medical stent; and atrack-and-lock mechanism having a shape substantially matching the shapeof said links so as to substantially prevent said links from moving insuch a way as to reduce the radius of the medical stent.
 2. The medicalstent as claimed in claim 1, wherein said plurality of links aremultiple electrical conductors, said multiple electrical conductorsforming a pattern to substantially prevent the self-deploying medicalstent from creating an imaging artifact.
 3. The medical stent as claimedin claim 1, wherein said plurality of links are multiple electricalconductors, said multiple electrical conductors forming a pattern tosubstantially allow imaging of a volume within the stent.
 4. The medicalstent as claimed in claim 1, wherein said plurality of links aremultiple electrical conductors, said multiple electrical conductorsforming a pattern to substantially prevent the self-deploying medicalstent from creating an imaging artifact and substantially allow imagingof a volume within the stent.
 5. The medical stent as claimed in claim1, wherein each link is tantalum.
 6. The medical stent as claimed inclaim 1, wherein each link is nitinol.
 7. The medical stent as claimedin claim 1, wherein each link is stainless steel.
 8. The medical stentas claimed in claim 1, wherein each link is NbZr.
 9. The medical stentas claimed in claim 1, wherein each link is titanium.
 10. A medicalstent, comprising: a plurality of links, each link being connectedtogether so as to form a cylindrical shaped medical stent, each linkbeing shaped so as to be expandable upon application of heat, saidexpansion of said links causing an increase in a radius of the medicalstent; and a track-and-lock mechanism having a shape substantiallymatching the shape of said links so as to allow said links to move in asingle direction.
 11. The medical stent as claimed in claim 10, whereinsaid plurality of links are multiple electrical conductors, saidmultiple electrical conductors forming a pattern to substantiallyprevent the self-deploying medical stent from creating an imagingartifact.
 12. The medical stent as claimed in claim 10, wherein saidplurality of links are multiple electrical conductors, said multipleelectrical conductors forming a pattern to substantially allow imagingof a volume within the stent.
 13. The medical stent as claimed in claim10, wherein said plurality of links are multiple electrical conductors,said multiple electrical conductors forming a pattern to substantiallyprevent the self-deploying medical stent from creating an imagingartifact and substantially allow imaging of a volume within the stent.14. The medical stent as claimed in claim 10, wherein each link istantalum.
 15. The medical stent as claimed in claim 10, wherein eachlink is nitinol.
 16. The medical stent as claimed in claim 10, whereineach link is stainless steel.
 17. The medical stent as claimed in claim10, wherein each link is NbZr.
 18. The medical stent as claimed in claim10, wherein each link is titanium.